University of Genova, Department of Pharmacy, Viale Cembrano, 4, I-16148, Genova, Italy.
University of Genova, Department of Pharmacy, Viale Cembrano, 4, I-16148, Genova, Italy.
Anal Chim Acta. 2019 Jun 13;1058:9-17. doi: 10.1016/j.aca.2018.10.055. Epub 2018 Oct 26.
The present tutorial paper is aimed to analyse and critically discuss the consequences of row pre-processing (conversion of measurement units, derivatives, and standard normal variate transform) on the evaluation of final outcomes of chemometric data analysis. An in-depth focus on pre-processing effects both on the signal shape and on misinterpretation of results - a crucial and disregarded issue in the analytical field - is presented. It is shown how this preliminary step of data processing may lead, in many cases, to draw incongruous conclusions, not actually based on real information embodied within data, but on artefacts arising from the mathematical transforms. This tutorial is not limited to a description of the problem, it also introduces strategies and tools for overcoming such unwanted effects, allowing a direct interpretation of the importance of original variables to be performed, explaining the chemical information that actually characterises samples. The dangerous implications of row pre-processing on instrumental signals is demonstrated on real datasets coming from different analytical techniques: transmission and attenuated total reflection infrared spectroscopy, cyclic voltammetry, X-ray fluorescence spectroscopy, Raman spectroscopy, and ultraviolet-visible spectroscopy. Hence, the impact of this widespread problem in most of the branches of analytical chemistry is illustrated.
本教程论文旨在分析和批判性讨论行预处理（测量单位转换、导数和标准正态变量变换）对化学计量数据分析最终结果评估的影响。本文深入关注预处理对信号形状和结果误判的影响——这是分析领域中一个关键但被忽视的问题。结果表明，在许多情况下，数据处理的这一初步步骤可能导致得出不一致的结论，这些结论实际上不是基于数据中包含的真实信息，而是基于数学变换产生的假象。本教程不仅限于描述问题，还介绍了克服这些不良影响的策略和工具，允许直接解释原始变量的重要性，解释实际表征样品的化学信息。在行预处理对仪器信号的危险影响方面，我们以来自不同分析技术的真实数据集为例进行了演示：透射和衰减全反射红外光谱、循环伏安法、X 射线荧光光谱、拉曼光谱和紫外-可见光谱。因此，说明了这个在分析化学的大多数分支中普遍存在的问题的影响。
